Laser Package Having Multiple Emitters Configured on a Substrate Member

ABSTRACT

A method and device for emitting electromagnetic radiation at high power using nonpolar or semipolar gallium containing substrates such as GaN, AN, InN, InGaN, AlGaN, and AlInGaN, is provided. In various embodiments, the laser device includes plural laser emitters emitting green or blue laser light, integrated a substrate.

CROSS REFERENCE TO RELATED APPLICATION

This present application claims priority to U.S. Provisional Application61/435,578; filed Jan. 24, 2011 (Docket No. 027364-013600US), which ishereby incorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention is directed to optical devices and relatedmethods. More specifically, the present invention provides a method anddevice for emitting electromagnetic radiation at high power usingnonpolar or semipolar gallium containing substrates such as GaN, AN,InN, InGaN, AlGaN, and AlInGaN, and others. In various embodiments, alaser device

In the late 1800's, Thomas Edison invented the light bulb. Theconventional light bulb, commonly called the “Edison bulb,” has beenused for over one hundred years for a variety of applications includinglighting and displays. The conventional light bulb uses a tungstenfilament enclosed in a glass bulb sealed in a base, which is screwedinto a socket. The socket is coupled to an AC power or DC power source.The conventional light bulb can be found commonly in houses, buildings,and outdoor lightings, and other areas requiring light or displays.Unfortunately, drawbacks exist with the conventional light bulb:

-   -   The conventional light bulb dissipates more than 90% of the        energy used as thermal energy.    -   The conventional light bulb routinely fails due to thermal        expansion and contraction of the filament element.    -   The conventional light bulb emits light over a broad spectrum,        much of which is not perceived by the human eye.    -   The conventional light bulb emits in all directions, which is        undesirable for applications requiring strong directionality or        focus, e.g. projection displays, optical data storage, etc.

In 1960, the laser was demonstrated by Theodore H. Maiman at HughesResearch Laboratories in Malibu. This laser utilized a solid-state flashlamp-pumped synthetic ruby crystal to produce red laser light at 694 nm.By 1964, blue and green laser output was demonstrated by William Bridgesat Hughes Aircraft utilizing a gas laser design called an Argon ionlaser. The Ar-ion laser utilized a noble gas as the active medium andproduce laser light output in the UV, blue, and green wavelengthsincluding 351 nm, 454.6 nm, 457.9 nm, 465.8 nm, 476.5 nm, 488.0 nm,496.5 nm, 501.7 nm, 514.5 nm, and 528.7 nm. The Ar-ion laser had thebenefit of producing highly directional and focusable light with anarrow spectral output, but the efficiency, size, weight, and cost ofthe lasers were undesirable.

As laser technology evolved, more efficient lamp pumped solid statelaser designs were developed for the red and infrared wavelengths, butthese technologies remained a challenge for blue and green and bluelasers. Lamp pumped solid-state lasers were developed in the infrared,and the output wavelength was converted to the visible using specialtycrystals with nonlinear optical properties. A green lamp pumpedsolid-state lasers had 3 stages: electricity powers lamp, lamp excitesgain crystal, which lases at 1064 nm, 1064 nm goes into frequencyconversion crystal, which converts, to visible 532 nm. The resultinggreen and blue lasers were called “lamp pumped solid state lasers withsecond harmonic generation” (LPSS with SHG) and were more efficient thanAr-ion gas lasers, but were still too inefficient, large, expensive,fragile for broad deployment outside of specialty scientific and medicalapplications. Additionally, the gain crystal used in the solid-statelasers typically had energy storage properties, which made the lasersdifficult to modulate at high speeds, which limited its broaderdeployment.

To improve the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal, which lases at 1064 nm, 1064nm goes into frequency conversion crystal, which converts, to visible532 nm. The DPSS laser technology extended the life and improved theefficiency of the LPSS lasers, and further commercialization ensue intomore high-end specialty industrial, medical, and scientificapplications. The change to diode pumping increased the system cost andrequired précised temperature controls, leaving the laser withsubstantial size, power consumption, while not addressing the energystorage properties which made the lasers difficult to modulate at highspeeds.

As high power laser diodes evolved and new specialty SHG crystals weredeveloped, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are meant to improve the efficiency, costand size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging. Additionally, while thediode-SHG lasers have the benefit of being directly modulate-able, theysuffer from severe sensitivity to temperature which limits theirapplication.

High power direct diode lasers have been in existence for the past fewdecades, beginning with laser diodes based on the GaAs material system,then moving to the AlGaAsP and InP material systems. More recently, highpower lasers based on GaN operating in the short wavelength visibleregime have become of great interest. More specifically, laser diodesoperating in the violet, blue, and eventually green regimes areattracting attention due to their application in optical storage,display systems, and others. Currently, high power laser diodesoperating in these wavelength regimes are based on polar c-plane GaN.The conventional polar GaN based laser diodes have a number ofapplications, but unfortunately, the device performance is ofteninadequate.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method and device for emittingelectromagnetic radiation at high power using nonpolar or semipolargallium containing substrates such as GaN, AN, InN, InGaN, AlGaN, andAlInGaN, and others. In various embodiments, a laser device comprisesnumber of laser emitters, which emit green or blue laser, integratedonto a substrate.

In a specific embodiment, the present invention provides a laser device.The device includes a substrate containing gallium and nitrogenmaterial. The substrate has a surface region characterized by asemipolar or nonpolar orientation. The substrate has a front side and aback side. The device includes at least one active region positionedwithin the substrate and an array of N emitters overlaying the activeregion, N being greater than 3. The array of N emitters is substantiallyparallel to one another and positioned between the front and the backside. Each of the N emitters is configured to emit a radiation at thefront side. The array of N emitter is associated with a blue or a greenwavelength. The array of N emitters is characterized by an averageoperating power of at least 25 mW. Each of the N emitters ischaracterized by a length and a width. The length is at least 400 um andthe width is at least 1 um. The device also has at least one electrodeelectrically coupled to the array of N emitters. The device also has atleast one optical member positioned at the front side of the substratefor optically combining radiation from the emitters.

In an alternative embodiment, the present invention provides a laserdevice. The device has a substrate containing gallium and nitrogenmaterial. The substrate has a surface region characterized by asemipolar or nonpolar orientation. The substrate has a front side and aback side. The device has one or more active regions positioned withinthe substrate. The device has an array of N emitters overlaying the oneor more active regions, N being greater than 3. The array of N emittersis substantially parallel to one another and positioned between thefront and the back side. Each of the N emitters is configured to emit aradiation at the front side. The array of N emitter is associated with ablue or a green wavelength range. The array of N emitters ischaracterized by an average operating power of at least 25 mW. Each ofthe N emitters is characterized by a length and a width, the lengthbeing at least 400 um, and the width being at least 1 um. The one ormore electrodes is electrically coupled to the array of N emitters. Theone or more optical members is positioned at the front side of thesubstrate for optically collimating radiation from the emitters. Thedevice also has a heat sink thermally coupled to the first substrate.

In an alternative embodiment, the present invention provides a laserdevice. The device includes a substrate containing gallium and nitrogenmaterial. The substrate has a surface region characterized by asemipolar or nonpolar orientation. The substrate has a top side and abottom side. The device has an N number of active regions positionednear the top side of the first substrate, N being greater than 3, eachof the active regions comprises a doped region associated with a p type.The device has an array of N emitters overlaying the doped regions. Thearray of N emitters is substantially parallel to one another. Each ofthe N emitters is configured to emit a radiation at the front side. Thearray of N emitters is characterized by an average operating power of atleast 25 mW. Each of the N emitters is characterized by a length and awidth, the length being at least 400 um, and the width being at least 1um. The device has one or more electrodes electrically coupled to thearray of N emitters and one or more optical members positioned at thefront side of the substrate for optically collimating radiation from theemitters. The device has a submount characterized by a thermalemissivity of at least 0.6.

In a specific embodiment, the device also includes one or more opticalmembers positioned at the front side of the substrate for opticallycombining radiation from the emitters.

Additional benefits are achieved over pre-existing techniques using thepresent invention. In particular, the present invention enables acost-effective optical device for laser applications, including laserbar for projectors, and the like. In a specific embodiment, the presentoptical device can be manufactured in a relatively simple and costeffective manner. Depending upon the embodiment, the present apparatusand method can be manufactured using conventional materials and/ormethods according to one of ordinary skill in the art. The present laserdevice uses a nonpolar or semipolar gallium nitride material capable ofachieving a violet or blue or green emission, among others. In one ormore embodiments, the laser device is capable of emitting longwavelengths such as those ranging from about 430 nm to 470 nm for theblue wavelength region or 500 nm to about 540 nm for the greenwavelength region, but can be others such as the violet region. Ofcourse, there can be other variations, modifications, and alternatives.Depending upon the embodiment, one or more of these benefits may beachieved. These and other benefits may be described throughout thepresent specification and more particularly below.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the latter portions of thespecification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating an optical device accordingto an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a laser device according to anembodiment of the present invention.

FIG. 3 is a simplified diagram illustrating a laser device having aplurality of emitters according to an embodiment of the presentinvention.

FIG. 4 is a simplified diagram illustrating a front view of a laserdevice with multiple cavity members according to an embodiment of thepresent invention.

FIGS. 5A and 5B are diagrams illustrating a laser package having“p-side” facing up according to an embodiment of the present invention.

FIGS. 6A and 6B are simplified diagram illustrating a laser packagehaving “p-side” facing down according to an embodiment of the presentinvention.

FIG. 7 is a simplified diagram illustrating an individually addressablelaser package according to an embodiment of the present invention.

FIG. 8 is a simplified diagram illustrating a laser bar having apatterned bonding substrate according to an embodiment of the presentinvention.

FIG. 9 is a simplified diagram illustrating laser bars configured withoptical combiners according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides high power GaN-based laser devices andrelated methods for making and using these laser devices. Specifically,laser devices are configured to operate with 0.5 to 5 W or 5 to 20 W ofoutput power in the blue or green wavelength regimes. The laser devicesare manufactured from bulk nonpolar or semipolar gallium and nitrogencontaining substrates. As mentioned above, the output wavelength of thelaser devices can be in the blue wavelength region of 430-475 nm and thegreen wavelength region 500-545 nm. Laser devices according toembodiments of the present invention can also operate in wavelengthssuch as violet (395 to 425 nm) and blue-green (475-505 nm). The laserdevices can be used in various applications, such as projection systemwhere a high power laser is used to project video content.

FIG. 1 is a simplified diagram illustrating an optical device. As anexample, the optical device includes a gallium nitride substrate member101 having a crystalline surface region characterized by a semipolar ornonpolar orientation. For example, the gallium nitride substrate memberis a bulk GaN substrate characterized by having a nonpolar or semipolarcrystalline surface region, but can be others. The bulk GaN substratemay have a surface dislocation density below 10⁵ cm⁻² or 10E5 to 10E7cm−2. The nitride crystal or wafer may comprise Al_(x)In_(y)Ga_(1-x-y)N,where 0≦x, y, x+y≦1. In one specific embodiment, the nitride crystalcomprises GaN. In one or more embodiments, the GaN substrate hasthreading dislocations, at a concentration between about 10⁵ cm⁻² andabout 10⁸ cm⁻², in a direction that is substantially orthogonal oroblique with respect to the surface. In various embodiments, the GaNsubstrate is characterized by a nonpolar orientation (e.g., m-plane),where waveguides are oriented in the c-direction or substantiallyorthogonal to the a-direction.

In certain embodiments, GaN surface orientation is substantially in the{20-21} orientation, and the device has a laser stripe region formedoverlying a portion of the off-cut crystalline orientation surfaceregion. For example, the laser stripe region is characterized by acavity orientation substantially in a projection of a c-direction, whichis substantially normal to an a-direction. In a specific embodiment, thelaser strip region has a first end 107 and a second end 109. In apreferred embodiment, the device is formed on a projection of ac-direction on a {20-21} gallium and nitrogen containing substratehaving a pair of cleaved mirror structures, which face each other.

In a preferred embodiment, the device has a first cleaved facet providedon the first end of the laser stripe region and a second cleaved facetprovided on the second end of the laser stripe region. In one or moreembodiments, the first cleaved is substantially parallel with the secondcleaved facet. Mirror surfaces are formed on each of the cleavedsurfaces. The first cleaved facet comprises a first mirror surface. In apreferred embodiment, the first mirror surface is provided by a top-sideskip-scribe scribing and breaking process. The scribing process can useany suitable techniques, such as a diamond scribe or laser scribe orcombinations. In a specific embodiment, the first mirror surfacecomprises a reflective coating. The reflective coating is selected fromsilicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia,including combinations, and the like. The first mirror surface can alsohave an anti-reflective coating.

Also in a preferred embodiment, the second cleaved facet comprises asecond mirror surface. The second mirror surface is provided by a topside skip-scribe scribing and breaking process according to a specificembodiment. Preferably, the scribing is diamond scribed or laser scribedor the like. In a specific embodiment, the second mirror surfacecomprises a reflective coating, such as silicon dioxide, hafnia, andtitania, tantalum pentoxide, zirconia, combinations, and the like. In aspecific embodiment, the second mirror surface has an anti-reflectivecoating.

In a specific embodiment on a nonpolar Ga-containing substrate, thedevice is characterized by a spontaneously emitted light is polarized insubstantially perpendicular to the c-direction. In a preferredembodiment, the spontaneously emitted light is characterized by apolarization ratio of greater than 0.1 to about 1 perpendicular to thec-direction. In a preferred embodiment, the spontaneously emitted lightcharacterized by a wavelength ranging from about 430 nanometers to about470 nm to yield a blue emission, or about 500 nanometers to about 540nanometers to yield a green emission, and others. For example, thespontaneously emitted light can be violet (e.g., 395 to 420 nanometers),blue (e.g., 430 to 470 nm); green (e.g., 500 to 540 nm), or others. In apreferred embodiment, the spontaneously emitted light is highlypolarized and is characterized by a polarization ratio of greater than0.4. In another specific embodiment on a semipolar {20-21} Ga-containingsubstrate, the device is also characterized by a spontaneously emittedlight is polarized in substantially parallel to the a-direction orperpendicular to the cavity direction, which is oriented in theprojection of the c-direction.

In a specific embodiment, the present invention provides an alternativedevice structure capable of emitting 501 nm and greater light in a ridgelaser embodiment. The device is provided with one or more of thefollowing epitaxially grown elements:

an n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Sidoping level of 5E17 to 3E18 cm−3

an n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 2% and 10% and thickness from 20 to 200 nm

multiple quantum well active region layers comprised of at least two2.0-8.5 nm InGaN quantum wells separated by 1.5 nm and greater, andoptionally up to about 12 nm, GaN or InGaN barriers

a p-side SCH layer comprised of InGaN with molar a fraction of indium ofbetween 1% and 10% and a thickness from 15 nm to 100 nm or an upperGaN-guide layer

an electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 6% and 22% and thickness from 5 nm to 20 nm anddoped with Mg.

a p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 2E17 cm−3 to 2E19 cm−3

a p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E19 cm−3 to 1E21 cm−3

FIG. 2 is a cross-sectional view of a laser device 200. As shown, thelaser device includes gallium nitride substrate 203, which has anunderlying n-type metal back contact region 201. For example, thesubstrate 203 may be characterized by a semipolar or nonpolarorientation. The device also has an overlying n-type gallium nitridelayer 205, an active region 207, and an overlying p-type gallium nitridelayer structured as a laser stripe region 209. Each of these regions isformed using at least an epitaxial deposition technique of metal organicchemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), orother epitaxial growth techniques suitable for GaN growth. The epitaxiallayer is a high quality epitaxial layer overlying the n-type galliumnitride layer. In some embodiments the high quality layer is doped, forexample, with Si or O to form n-type material, with a dopantconcentration between about 10¹⁶ cm³ and 10²⁰ cm³.

An n-type Al_(u)In_(v)Ga_(1-u-v)N layer, where 0≦u, v, u+v≦1, isdeposited on the substrate. The carrier concentration may lie in therange between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³. The deposition may beperformed using metalorganic chemical vapor deposition (MOCVD) ormolecular beam epitaxy (MBE).

For example, the bulk GaN substrate is placed on a susceptor in an MOCVDreactor. After closing, evacuating, and back-filling the reactor (orusing a load lock configuration) to atmospheric pressure, the susceptoris heated to a temperature between about 1000 and about 1200 degreesCelsius in the presence of a nitrogen-containing gas. The susceptor isheated to approximately 900 to 1200 degrees Celsius under flowingammonia. A flow of a gallium-containing metalorganic precursor, such astrimethylgallium (TMG) or triethylgallium (TEG) is initiated, in acarrier gas, at a total rate between approximately 1 and 50 standardcubic centimeters per minute (sccm). The carrier gas may comprisehydrogen, helium, nitrogen, or argon. The ratio of the flow rate of thegroup V precursor (ammonia) to that of the group III precursor(trimethylgallium, triethylgallium, trimethylindium, trimethylaluminum)during growth is between about 2000 and about 12000. A flow of disilanein a carrier gas, with a total flow rate of between about 0.1 and 10sccm, is initiated.

In one embodiment, the laser stripe region is p-type gallium nitridelayer 209. The laser stripe is provided by a dry etching process, butwet etching can be used. The dry etching process is an inductivelycoupled process using chlorine bearing species or a reactive ion etchingprocess using similar chemistries. The chlorine bearing species arecommonly derived from chlorine gas or the like. The device also has anoverlying dielectric region, which exposes 213 contact region. Thedielectric region is an oxide such as silicon dioxide or siliconnitride, and a contact region is coupled to an overlying metal layer215. The overlying metal layer is preferably a multilayered structurecontaining gold and platinum (Pt/Au) or nickel gold (Ni/Au).

Active region 207 preferably includes one to ten quantum well regions ora double heterostructure region for light emission. Following depositionof the n-type Al_(u)In_(v)Ga_(1-u-v)N layer to achieve a desiredthickness, an active layer is deposited. The quantum wells arepreferably InGaN with GaN, AlGaN, InAlGaN, or InGaN barrier layersseparating them. In other embodiments, the well layers and barrierlayers comprise Al_(w)In_(x)Ga_(1-w-x)N and Al_(y)In_(z)Ga_(1-y-z)N,respectively, where 0≦w, x, y, z, w+x, y+z≦1, where w<u, y and/or x>v, zso that the bandgap of the well layer(s) is less than that of thebarrier layer(s) and the n-type layer. The well layers and barrierlayers each have a thickness between about 1 nm and about 20 nm. Thecomposition and structure of the active layer are chosen to providelight emission at a preselected wavelength. The active layer may be leftundoped (or unintentionally doped) or may be doped n-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. The electron-blocking layer maycomprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≦s, t, s+t≦1, with a higherbandgap than the active layer, and may be doped p-type. In one specificembodiment, the electron blocking layer includes AlGaN. In anotherembodiment, the electron blocking layer includes an AlGaN/GaNsuper-lattice structure, comprising alternating layers of AlGaN and GaN,each with a thickness between about 0.2 nm and about 5 nm.

As noted, the p-type gallium nitride structure is deposited above theelectron blocking layer and active layer(s). The p-type layer may bedoped with Mg, to a level between about 10¹⁶ cm⁻³ and 10²² cm⁻³, with athickness between about 5 nm and about 1000 nm. The outermost 1-50 nm ofthe p-type layer may be doped more heavily than the rest of the layer,so as to enable an improved electrical contact. The device also has anoverlying dielectric region, for example, silicon dioxide, which exposes213 contact region.

The metal contact is made of suitable material such as silver, gold,aluminum, nickel, platinum, rhodium, palladium, chromium, or the like.The contact may be deposited by thermal evaporation, electron beamevaporation, electroplating, sputtering, or another suitable technique.In a preferred embodiment, the electrical contact serves as a p-typeelectrode for the optical device. In another embodiment, the electricalcontact serves as an n-type electrode for the optical device. The laserdevices illustrated in FIGS. 1 and 2 and described above are typicallysuitable for relative low-power applications.

In various embodiments, the present invention realizes high output powerfrom a diode laser is by widening one or more portions of the lasercavity member from the single lateral mode regime of 1.0-3.0 μm to themulti-lateral mode range 5.0-20 μm. In some cases, laser diodes havingcavities at a width of 50 μm or greater are employed.

The laser stripe length, or cavity length ranges from 300 to 3000 μm andemploys growth and fabrication techniques such as those described inU.S. patent application Ser. No. 12/759,273, filed Apr. 13, 2010, whichis incorporated by reference herein. As an example, laser diodes arefabricated on nonpolar or semipolar gallium containing substrates, wherethe internal electric fields are substantially eliminated or mitigatedrelative to polar c-plane oriented devices. It is to be appreciated thatreduction in internal fields often enables more efficient radiativerecombination. Further, the heavy hole mass is expected to be lighter onnonpolar and semipolar substrates, such that better gain properties fromthe lasers can be achieved.

One difficulty with fabricating high-power GaN-based lasers with widecavity designs is a phenomenon where the optical field profile in thelateral direction of the cavity becomes asymmetric where there are localbright regions and local dim regions. Such behavior is often referred toas filamenting and can be induced by lateral variations in the index ofrefraction or thermal profile, which alters the mode guidingcharacteristics. Such behavior can also be a result of non-uniformitiesin the local gain/loss caused by non-uniform injection of carriers intothe active region or current crowding where current is preferentiallyconducted through the outer regions of the laser cavity. That is, thecurrent injected through the p-side electrode tends towards the edge ofthe etched p-cladding ridge/stripe required for lateral waveguiding, andthen conducted downward where the holes recombine with electronsprimarily near the side of the stripe. Regardless of the cause, suchfilamenting or non-symmetric optical field profiles can lead to degradedlaser performance as the stripe width is increased.

FIG. 3 is a simplified diagram illustrating a laser device having aplurality of emitters according to an embodiment of the presentinvention. As shown in FIG. 3, a laser device includes a substrate and aplurality of emitters. Each cavity member, in conjunction with theunderlying active region within the substrate and other electricalcomponents, is a part of a laser diode. The laser device in FIG. 3includes three laser diodes, each having its emitter or cavity member(e.g., cavity member 302 functions a waveguide of a laser diode) andsharing the substrate 301, which contains one or more active regions. Invarious embodiments, the active regions include quantum wells or adouble hetereostructure for light emission. The cavity members functionas waveguides. A device with multiple cavity members integrated on asingle substrate and the method of manufacturing thereof are describedin the U.S. Provisional Patent Application No. 61/345,561, filed May 17,2010, which is hereby incorporated by reference.

The substrate shown in FIG. 3 contains gallium and nitrogen materialfabricated from nonpolar or semipolar bulk GaN substrate. The cavitymembers as shown are arranged in parallel to one another. For example,cavity member 301 includes a front mirror and a back mirror, similar tothe cavity member 101 illustrated in FIG. 1. Each of the laser cavitiesis characterized by a cavity width, w, ranging from about 1 to about 6um. Such arrangement of cavity members increases the effective stripewidth while assuring that the cavity members are uniformly pumped. In anembodiment, cavity members are characterized by a substantially equallength and width.

Depending on the application, a high power laser device can have anumber of cavity members. The number of cavity members, n, can rangefrom 2 to 5, 10, or even 20. The lateral spacing, or the distanceseparating one cavity member from another, can range from 2 um to 25 um,depending upon the requirements of the laser diode. In variousembodiments, the length of the cavity members can range from 300 um to2000 um, an in some cases as much as 3000 um.

In a preferred embodiment, laser emitters (e.g., cavity members asshown) are arranged as a linear array on a single chip to emit blue orgreen laser light. The emitters are substantially parallel to oneanother, and they can be separated by 3 um to 15 um, by 15 um to 75 um,by 75 um to 150 um, or by 150 um to 300 um. The number of emitters inthe array can vary from 3 to 15 or from 15 to 30, or from 30 to 50, orfrom 50 to 100, or more than 100. Each emitter may produce an averageoutput power of 25 to 50 mW, 50 to 100 mW, 100 to 250 mW, 250 to 500 mW,500 to 1000 mW, or greater than 1 W. Thus the total output power of thelaser device having multiple emitters can range from 200 to 500 mW, 500to 1000 mW, 1-2 W, 2-5 W, 5-10 W, 10-20 W, and greater than 20 W.

With current technology, the dimension of the individual emitters wouldbe widths of 1.0 to 3.0 um, 3.0 to 6.0 um, 6.0 to 10.0 um, 10 to 20.0um, and greater than 20 um. The lengths range from 400 um to 800 um, 800um to 1200 um, 1200 um to 1600 um, or greater than 1600 um.

The cavity member has a front end and a back end. The laser device isconfigured to emit laser beam through the front mirror at the front end.The front end can have anti-reflective coating or no coating at all,thereby allowing radiation to pass through the mirror without excessivereflectivity. Since no laser beam is to be emitted from the back end ofthe cavity member, the back mirror is configured to reflect theradiation back into the cavity. For example, the back mirror includeshighly reflective coating with a reflectivity greater than 85% or 95%.

FIG. 4 is a simplified diagram illustrating a front view of a laserdevice with multiple cavity members. As shown in FIG. 4, an activeregion 307 can be seen as positioned in the substrate 301. The cavitymember 302 as shown includes a via 306. Vias are provided on the cavitymembers and opened in a dielectric layer 303, such as silicon dioxide.The top of the cavity members with vias can be seen as laser ridges,which expose electrode 304 for an electrical contact. The electrode 304includes p-type electrode. In a specific embodiment, a common p-typeelectrode is deposited over the cavity members and dielectric layer 303,as illustrated in FIG. 4.

The cavity members are electrically coupled to each other by theelectrode 304. The laser diodes, each having an electrical contactthrough its cavity member, share a common n-side electrode. Depending onthe application, the n-side electrode can be electrically coupled to thecavity members in different configurations. In a preferred embodiment,the common n-side electrode is electrically coupled to the bottom sideof the substrate. In certain embodiments, re-contact is on the top ofthe substrate, and the connection is formed by etching deep down intothe substrate from the top and then depositing metal contacts. Forexample, laser diodes are electrically coupled to one another in aparallel configuration. In this configuration, when current is appliedto the electrodes, all laser cavities can be pumped relatively equally.Further, since the ridge widths will be relatively narrow in the 1.0 to5.0 um range, the center of the cavity member will be in close vicinityto the edges of the ridge (e.g., via) such that current crowding ornon-uniform injection will be mitigated. Most importantly, filamentingcan be prevented and the lateral optical field profile can be symmetricin such narrow cavities as shown in FIG. 2A.

It is to be appreciated that the laser device with multiple cavitymembers has an effective ridge width of n×w, which could easily approachthe width of conventional high power lasers having a width in the 10 to50 um range. Typical lengths of this multi-stripe laser could range from400 um to 2000 um, but could be as much as 3000 um. A schematicillustration of a conventional single stripe narrow ridge emitterintended for lower power applications of 5 to 500 mW is shown in FIG. 1with the resulting laterally symmetric field profile in FIG. 2A. Aschematic diagram of a multi-stripe emitter as an example thisembodiment intended for operation powers of 0.5 to 10 W is shown in FIG.2.

The laser device illustrated in FIGS. 3 and 4 has a wide range ofapplications. For example, the laser device can be coupled to a powersource and operate at a power level of 0.5 to 10 W. In certainapplications, the power source is specifically configured to operate ata power level of greater than 10 W. The operating voltage of the laserdevice can be less than 5V, 5.5V, 6V, 6.5V, 7V, and other voltages. Invarious embodiments, the wall plug efficiency (e.g., totalelectrical-to-optical power efficiency) can be 15% or greater, 20% orgreater, 25% or greater, 30% or greater, 35% or greater.

A typical application of laser devices is to emit a single ray of laserlight. As the laser device includes a number of emitters, an opticalmember is needed to combine or collimate output from the emitters. FIGS.5A and 5B are diagrams illustrating a laser package having“p-side”facing up. As shown in FIG. 5A, a laser bar is mounted on asubmount. The laser bar includes an array of emitters (e.g., asillustrated in FIGS. 3 and 4). The laser bar is attached the submount,which is positioned between the laser bar and a heat sink. It is to beappreciated that the submount allows the laser bar (e.g., galliumnitride material) to securely attached to the heat sink (e.g., coppermaterial with high thermal emissivity). In various embodiments, submountincludes aluminum nitride material characterized by a high thermalconductivity. For example, thermal conductivity for aluminum nitridematerial used in the submount can exceed 200 W/(mk). Other types ofmaterials can be used for submount as well, such as diamond, coppertungsten alloy, beryllium oxide. In a preferred embodiment, the submountmaterials are used to compensate coefficient of thermal expansion (CTE)mismatch between the laser bar and the heat sink.

In FIG. 5A, the “p-side” (i.e., the side with emitters) of the laser barfaces upward and thus is not coupled to the submount. The p-side of thelaser bar is electrically coupled to the anode of a power source througha number of bonding wires. Since both the submount and the heat sink areconductive, the cathode electrode of the power source can beelectrically coupled to the other side of the laser bar through thesubmount and the heat sink.

In a preferred embodiment, the array of emitters of the laser bar ismanufactured from a gallium nitride substrate. The substrate can havesurface characterized by a semi-polar or non-polar orientation. Thegallium nitride material allows the laser device to be packaged withouthermetic sealing. More specifically, by using the gallium nitridematerial, the laser bar is substantially free from AlGaN or InAlGaNcladdings. When the emitter is substantially in proximity to p-typematerial, the laser device is substantially free from p-type AlGaN orp-type InAlGaN material. Typically, AlGaN or InAlGaN claddings areunstable when operating in normal atmosphere, as they interact withoxygen. To address this problem, conventional laser devices comprisingAlGaN or InAlGaN material are hermetically sealed to prevent interactionbetween AlGaN or InAlGaN and air. In contrast, since AlGaN or InAlGaNcladdings are not present in laser devices according to embodiments ofthe present invention, the laser devices does not need to behermetically packaged. The cost of manufacturing laser devices andpackages according to embodiments of the present invention can be lowerthan that of conventional laser devices by eliminating the need forhermetic packaging.

FIG. 5B is a side view diagram of the laser device illustrated in FIG.5A. The laser bar is mounted on the submount, and the submount ismounted on the heat side. As explained above, since the laser barincludes a number of emitters, a collimating lens is used to combine theemitted laser to form a desired laser beam. In a preferred embodiment,the collimating lens is a fast-axis collimating (FAC) lens that ischaracterized by a cylindrical shape.

FIGS. 6A and 6B are simplified diagram illustrating a laser packagehaving “p-side” facing down according to an embodiment of the presentinvention. In FIG. 6A, a laser bar is mounted on a submount. The laserbar includes an array of emitters (e.g., as illustrated in FIGS. 3 and4). In a preferred embodiment, the laser bar includes substratecharacterized by a semipolar or non-polar orientation. The laser bar isattached the submount, which is positioned between the laser bar and aheat sink. The “p-side” (i.e., the side with emitters) of the laser barfaces downed and thus is directly coupled to the submount. The p-side ofthe laser bar is electrically coupled to the anode of a power sourcethrough the submount and/or the heat sink. The other side of the laserbar is electrically coupled to the cathode of the power source through anumber of bonding wires.

FIG. 6B is a side view diagram of the laser device illustrated in FIG.6A. As shown, the laser bar is mounted on the submount, and the submountis mounted on the heat side. As explained above, since the laser barincludes a number of emitters, a collimating lens is used to combine theemitted laser to form a desired laser beam. In a preferred embodiment,the collimating lens is a fast-axis collimating (FAC) lens that ischaracterized by a cylindrical shape.

FIG. 7 is a simplified diagram illustrating an individually addressablelaser package according to an embodiment of the present invention. Thelaser bar includes a number of emitters separated by ridge structures.Each of the emitter is characterized by a width of about 90-200 um, butit is to be understood that other dimensions are possible as well. Eachof the laser emitters includes a pad for p-contact wire bond. Forexample, electrodes can be individually coupled to the emitters so thatit is possible to selectively turning a emitter on and off. Theindividually addressable configuration shown in FIG. 7 provides numerousbenefits. For example, if a laser bar having multiple emitters is notindividually addressable, laser bar yield during manufacturing can be aproblem, since many individual laser devices need to be good in orderfor the bar to pass, and that means laser bar yield will be lower thanindividual emitter yield. In addition, setting up the laser bar withsingle emitter addressability makes it possible to screen each emitter.In a certain embodiments, a control module is electrically coupled tothe laser for individually controlling devices of the laser bar.

FIG. 8 is a simplified diagram illustrating a laser bar having apatterned bonding substrate according to an embodiment of the presentinvention. As shown, laser devices are characterized by a width ofaround 30 um. Depending on the application, other widths are possible aswell. Laser emitters having pitches smaller than about 90 microns aredifficult to form wire bonds. In various embodiments, a patternedbonding substrate is used for forming contacts. For example, the patternbonding substrates allows for the width to be as low as 10-30 um.

FIG. 9 is a simplified diagram illustrating laser bars configured withan optical combiner according to embodiments of the present invention.As shown, the diagram includes a package or enclosure for multipleemitters. Each of the devices is configured on a single ceramic ormultiple chips on a ceramic, which are disposed on common heatsink. Asshown, the package includes all free optics coupling, collimators,mirrors, spatially or polarization multiplexed for free space output orrefocused in a fiber or other waveguide medium. As an example, thepackage has a low profile and may include a flat pack ceramic multilayeror single layer. The layer may include a copper, a copper tungsten basesuch as butterfly package or covered CT mount, Q-mount, or others. In aspecific embodiment, the laser devices are soldered on CTE matchedmaterial with low thermal resistance (e.g., AN, diamond, diamondcompound) and forms a sub-assembled chip on ceramics. The sub-assembledchip is then assembled together on a second material with low thermalresistance such as copper including, for example, active cooling (i.e.,simple water channels or micro channels), or forming directly the baseof the package equipped with all connections such as pins. The flatpackis equipped with an optical interface such as window, free space optics,connector or fiber to guide the light generated and a coverenvironmentally protective.

In a specific embodiment, the package can be used in a variety ofapplications. The applications include power scaling (modularpossibility), spectral broadening (select lasers with slight wavelengthshift for broader spectral characteristics). The application can alsoinclude multicolor monolithic integration such as blue-blue, blue-green,RGB (Red-Blue-Green), and others.

In a specific embodiment, the present laser device can be configured ona variety of packages. As an example, the packages include TO9 Can, TO56Can, flat package(s), CS-Mount, G-Mount, C-Mount, micro-channel cooledpackage(s), and others. In other examples, the multiple laserconfiguration can have an operating power of 1.5 Watts, 3, Watts, 6Watts, 10 Watts, and greater. In an example, the present optical device,including multiple emitters, are free from any optical combiners, whichlead to inefficiencies. In other examples, optical combiners may beincluded and configured with the multiple emitter devices. Additionally,the plurality of laser devices (i.e., emitters) may be an array of laserdevice configured on non-polar oriented GaN or semi-polar oriented GaNor any combination of these, among others.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k 1) planewherein h=k=0, and 1 is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k 1) plane wherein 1=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k 1) plane wherein 1=0, and atleast one of h and k is non-zero). Of course, there can be othervariations, modifications, and alternatives.

In other examples, the present device is operable in an environmentcomprising at least 150,000 ppmv oxygen gas. The laser device issubstantially free from AlGaN or InAlGaN claddings. The laser device issubstantially free from p-type AlGaN or p-type InAlGaN claddings. Eachof the emitter comprises a front facet and a rear facet, the front facetbeing substantially free from coatings. Each of the emitter comprises afront facet and a rear facet, the rear facet comprising a reflectivecoating. In other examples, the device also has a micro-channel coolerthermally coupled to the substrate. The device also has a submountcharacterized by a coefficient of thermal expansion (CTE) associatedwith the substrate and a heat sink. The submount coupled to thesubstrate, the submount comprises aluminum nitride material, BeO,diamond, composite diamond, or combinations In a specific embodiment,the substrate is glued onto a submount, the submount being characterizedby a heat conductivity of at least 200 W/(mk). The substrate comprisesone or more cladding regions. The one or more optical members comprise afast-axis collimation lens. The laser device is characterized by aspectral width of at least 4 nm. In a specific example, the number N ofemitters can range between 3 and 15, 15 and 30, 30 and 50, and can begreater than 50. In other examples, each of the N emitters produces anaverage output power of 25 to 50 mW, produces an average output power of50 to 100 mW, produces an average output power of 100 to 250 mW,produces an average output power of 250 to 500 mW, or produces anaverage output power of 500 to 1000 mW. In a specific example, each ofthe N emitters produces an average output power greater than 1 W. In anexample, each of the N emitters is separated by 3 um to 15 um from oneanother or separated by 15 um to 75 um from one another or separated by75 um to 150 um from one another or separated by 150 um to 300 um fromone another.

In yet an alternative specific embodiment, the present inventionprovides an optical device, e.g., laser. The device includes a galliumand nitrogen containing material having a surface region, which ischaracterized by a semipolar surface orientation within 5 degrees of oneof the following (10-11), (10-1-1), (20-21), (20-2-1), (30-31),(30-3-1), (40-41), or (40-4-1). The device also has a first waveguideregion configured in a first direction, which is a projection of ac-direction overlying the surface region of the gallium and nitrogencontaining material in a specific embodiment. The device also has asecond waveguide region coupled to the first waveguide region and isconfigured in a second direction overlying the surface region of thegallium and nitrogen containing material. In a preferred embodiment, thesecond direction is different from the first direction and substantiallyparallel to the a-direction. In a preferred embodiment, the first andsecond waveguide regions are continuous, are formed as a singlecontinuous waveguide structure, and are formed together duringmanufacture of the waveguides. Of course, there can be other variations,modifications, and alternatives.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

1. A laser device comprising: a substrate containing gallium andnitrogen material, the substrate have a surface region characterized bya semipolar or nonpolar orientation, the substrate having a front sideand a back side; at least one active region positioned within thesubstrate; an array of N emitters overlaying the active region, N beinggreater than 3, the array of N emitters being substantially parallel toone another and positioned between the front and the back side, each ofthe N emitters being configured to emit a radiation at the front side,the array of N emitter being associated with a blue or a greenwavelength, the array of N emitters being characterized by an averageoperating power of at least 25 mW, each of the N emitters beingcharacterized by a length and a width, the length being at least 400 um,the width being at least 1 um; at least one electrode electricallycoupled to the array of N emitters; and at least one optical memberpositioned at the front side of the substrate for optically combiningradiation from the emitters.
 2. The device of claim 1 wherein the laserdevice is operable in an environment comprising at least 150,000 ppmvoxygen gas; whereupon the laser device is substantially free fromefficiency degradation over a time period from the oxygen gas.
 3. Thedevice of claim 1 wherein the laser device is substantially free fromAlGaN or InAlGaN claddings; wherein each of the emitter comprises afront facet and a rear facet, the front facet being substantially freefrom coatings.
 4. The device of claim 1 further comprising amicro-channel cooler thermally coupled to the substrate; and furthercomprising a submount characterized by a coefficient of thermalexpansion (CTE) associated with the substrate and a heat sink.
 5. Thedevice of claim 1 further comprising a submount coupled to thesubstrate, the submount is made of a material including at least one ofaluminum nitride, BeO, diamond, composite diamond, or combinations. 6.The device of claim 1 further wherein the substrate is glued onto asubmount, the submount being characterized by a heat conductivity of atleast 200 W/(mk).
 7. The device of claim 1 wherein the substratecomprises one or more cladding regions.
 8. The device of claim 1 whereinthe one or more optical members comprise a fast-axis collimation lens.9. The device of claim 1 wherein the laser device is characterized by aspectral width of at least 4 nm; wherein N ranges between 3 and
 50. 10.The device of claim 1 wherein each of the N emitters produces an averageoutput power of 25 to 1000 mW.
 11. The device of claim 1 wherein each ofthe N emitters produces an average output power greater than 1 W. 12.The device of claim 1 wherein the N emitters being separated by 3 um to300 um from one another.
 13. A laser device comprising: a substratecontaining gallium and nitrogen material, the substrate have a surfaceregion characterized by a semipolar or nonpolar orientation, thesubstrate having a front side and a back side; one or more activeregions positioned within the substrate; an array of N emittersoverlaying the one or more active regions, N being greater than 3, thearray of N emitters being substantially parallel to one another andpositioned between the front and the back side, each of the N emittersbeing configured to emit a radiation at the front side, the array of Nemitter being associated with a blue or a green wavelength, the array ofN emitters being characterized by an average operating power of at least25 mW, each of the N emitters being characterized by a length and awidth, the length being at least 400 um, the width being at least 1 um;one or more electrodes electrically coupled to the array of N emitters;one or more optical members positioned at the front side of thesubstrate for optically collimating radiation from the emitters; a heatsink thermally coupled to the first substrate.
 14. The device of claim13 further comprising a second substrate stacking on top of the firstsubstrate.
 15. The device of claim 13 further comprising a secondsubstrate stacking by side of the first substrate.
 16. A laser devicecomprising: a substrate containing gallium and nitrogen material, thesubstrate have a surface region characterized by a semipolar or nonpolarorientation, the substrate having a top side and a bottom side; an Nnumber of active regions positioned near the top side of the firstsubstrate, N being greater than 3, each of the active regions comprisesa doped region associated with a p type; an array of N emittersoverlaying the doped regions, the array of N emitters beingsubstantially parallel to one another, each of the N emitters beingconfigured to emit a radiation at the front side, the array of Nemitters being characterized by an average operating power of at least25 mW, each of the N emitters being characterized by a length and awidth, the length being at least 400 um, the width being at least 1 um;one or more electrodes electrically coupled to the array of N emitters;one or more optical members positioned at the front side of thesubstrate for optically collimating radiation from the emitters; and asubmount characterized by a thermal emissivity of at least 0.6.
 17. Thedevice of claim 16 wherein the submount comprises diamond material orcopper tungsten alloy material or beryllium oxide material.
 18. Thedevice of claim 16 wherein the surface region is characterized by the{11-22}, {20-21}, or the {30-31} planes or within +/−5 degrees fromthese planes.
 19. The device of claim 16 wherein the submount isdirectly coupled to the top side of the substrate.
 20. The device ofclaim 16 wherein the submount is directly coupled to the bottom side ofthe substrate.
 21. The device of claim 16 wherein the submount isdirectly coupled to array of N emitters; wherein the one or more opticalmembers comprises a collimating lens.
 22. The device of claim 16 whereinthe laser device is characterized by an output wavelength of about505-550 nm or 425-475 nm.
 23. The device of claim 16 further comprisinga heat sink thermally coupled to the submount.
 24. The device of claim16 wherein the laser device is characterized by a peak wall plugefficiency of at least 25%; and further comprising one or more quantumwells positioned within the N number of active regions.
 25. A laserdevice comprising: a substrate, the substrate having a front side and aback side; at least one active region positioned within the substrate;an array of N emitters overlaying the active region, N being greaterthan 3, the array of N emitters being substantially parallel to oneanother and positioned between the front and the back side, each of theN emitters being configured to emit a radiation at the front side, thearray of N emitter being associated with a blue or a green wavelength,the array of N emitters being characterized by an average operatingpower, each of the N emitters being characterized by a length and awidth; at least one electrode electrically coupled to the array of Nemitters; and at least one optical member positioned at the front sideof the substrate for optically combining radiation from the emitters.